AN-1101: Application with SCALE-2 Gate Driver Cores

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AN-1101
Application Note
Application with SCALE™-2 and SCALE™-2+
Gate Driver Cores
Single and Dual-Channel SCALE™-2 and SCALE™-2+ IGBT and MOSFET Driver
Cores
Introduction and Overview
The SCALE™-2 and SCALE™-2+ IGBT and MOSFET gate driver cores are highly integrated low-cost
components which provide the user with the highest level of technology and functionality for industrial and
traction requirements. These features, coupled with their flexibility of design, have already made many power
converters highly successful. Nevertheless, SCALE-2 and SCALE-2+ gate driver cores are not plug-and-play
gate drivers. A minimum understanding of power electronics is therefore necessary to develop reliable inverter
systems with these cores.
This Application Note will highlight important design rules to help users and avoid qualification problems.
Moreover it will help to speed up the development time by showing detailed examples about how to design
SCALE-2 and SCALE-2+ gate driver cores successfully.
Considered SCALE-2 and SCALE-2+ gate driver cores are: 2SC0106T, 2SC0108T, 2SC0435T, 2SC0650P,
1SC2060P, 2SC0535T, 2SC0635T and 1SC0450.
Fig. 1 SCALE-2 and SCALE-2+ gate driver cores
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Application Note
Contents
Introduction and Overview ............................................................................................................ 1
Contents ......................................................................................................................................... 2
Nomenclature Information ............................................................................................................ 4
Applications with SCALE-2 Products .............................................................................................. 4
SCALE-2 in Different Topologies .................................................................................................... 4
Use of SCALE-2 gate driver cores in three-level or multilevel topologies.................................... 4
Use of a single SCALE-2 gate driver for paralleled IGBTs/MOSFETs .......................................... 5
Direct paralleling ................................................................................................................. 7
Application Circuits ........................................................................................................................ 7
Minimum pulse suppression for inputs INA and INB ................................................................ 7
Increase of the noise immunity at inputs INA and INB (excluding 2SC0635T) ........................... 8
Use of external optical interface with SCALE-2 gate drivers with internal electrical interface ....... 9
Half-bridge mode............................................................................................................... 10
External implementation of half-bridge mode ....................................................................... 11
External implementation of minimum channel interlock time.................................................. 12
Use of SOx fault outputs .................................................................................................... 12
Use of gate resistors .......................................................................................................... 13
VEx terminal characteristics ................................................................................................ 14
Required blocking capacitors C 1x and C 2x ............................................................................. 15
V CEsat detection with SCALE-2 gate driver cores (excluding 2SC0108T) ................................... 16
Disable V CEsat detection by SCALE-2 (excluding 2SC0106T and 2SC0108T) .............................. 20
Disabling the Advanced Active Clamping .............................................................................. 21
Rail-to-rail output and gate voltage clamping ....................................................................... 21
Paralleling a dual-channel driver to a single output ............................................................... 22
Disabling one channel for chopper applications .................................................................... 24
Position of the Gate Driver in the Converter................................................................................ 24
Driver placement on top of 17mm IGBT modules or close to high magnetic fields ................... 24
AC and DC bus bar ............................................................................................................ 25
PCB Layout ................................................................................................................................... 25
PCB thickness .................................................................................................................... 25
Separation of areas with different high-voltage potentials ..................................................... 26
Use of planes .................................................................................................................... 27
Clearance and creepage distances for PCBs ......................................................................... 28
Gate driver cores in applications at higher altitudes .............................................................. 28
Power Integrations’ Reference Designs ................................................................................ 29
Typical Application Failures ......................................................................................................... 30
Bibliography ................................................................................................................................. 31
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Application Note
Legal Disclaimer ........................................................................................................................... 31
Manufacturer ................................................................................................................................ 31
Power Integrations Worldwide High Power Customer Support Locations .................................. 32
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AN-1101
Application Note
Nomenclature Information
This Application Note is valid for the named SCALE-2 and SCALE-2+ products.
In the following sections, the “SCALE-2” designation also includes “SCALE-2+”. SCALE-2+ is therefore not
explicitly mentioned if not required.
Applications with SCALE-2 Products
A successful use of SCALE-2 gate driver cores is coupled with an appropriate overall design. The key points
listed below are success factors for the use of SCALE-2 gate drivers:
•
Topology (e.g. how to parallelize IGBT modules)
•
Schematics and right choice of components
•
Geometrical location of IGBT gate drivers (where to place gate drivers)
•
Magnetic field influences
•
Clearance and creepage distances
•
PCB layout
•
Use of standards
•
EMI considerations
SCALE-2 in Different Topologies
Use of SCALE-2 gate driver cores in three-level or multilevel topologies
During the operation of three-level converters, regular semiconductor commutation ensures that the inner
IGBTs/MOSFETs are not turned off when the outer IGBTs/MOSFETs are in the on-state in order to avoid the
full DC-link voltage being applied to the corresponding power semiconductors.
This situation must be considered when using Power Integrations’ SCALE-2 gate drivers. Such events could
happen if the protection function of the gate drivers detects a short circuit or in the case of power-supply
under-voltage. After fault detection, the gate driver turns the corresponding channel off immediately
(exceptions are 2SC0635T and 1SC0450, where a delay between secondary fault detection and IGBT turn-off
can be programmed, refer also to the corresponding product documentation /1/, /2/). The power
semiconductors are not usually designed to withstand the full DC-link voltage. Destruction of the power
semiconductor can consequently be prevented only if an adequate protection scheme is applied.
SCALE-2 Advanced Active Clamping protects the IGBTs/MOSFETs from excessive collector-emitter voltages in
such situations. It therefore obviates the need to provide a dedicated turn-off sequence for the driver channels
to be turned off in the fault condition - instead, the turn-off commands may be applied immediately after fault
feedback. It is recommended to apply a common turn-off command to all IGBT drivers within the converter to
achieve a stable system state after fault feedback.
Please also refer to Application Note AN-0901 /3/ or to the paper “Safe Driving of Multi-Level Converters Using
Sophisticated Gate Driver Technology” /5/ for more information.
Note: The under-voltage protection function of the SCALE-2 chipset cannot be disabled. The gate driver
channel is turned off as soon as an under-voltage event is detected on the primary or secondary side
(exceptions: 2SC0635T and 1SC0450, for which a delay can be programmed in case of a secondary-side fault).
The use of active clamping consequently offers the best protection. In such cases, however, Power
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Application Note
Integrations highly recommends testing the effectiveness of the active clamping function in the final converter
design.
Fig. 2 Three-level converter with use of Advanced Active Clamping
Use of a single SCALE-2 gate driver for paralleled IGBTs/MOSFETs
Advanced Active Clamping in parallel IGBT operation with one common driver core
Active clamping is a technique designed to partially turn on the power semiconductor as soon as the collectoremitter (drain-source) voltage exceeds a predefined threshold. The power semiconductor is then kept in linear
operation.
Basic active clamping topologies implement a single feedback path from the IGBT’s collector through transient
voltage suppressor devices (TVS) to the gate. Most SCALE-2 products support Power Integrations' Advanced
Active Clamping, where feedback is also provided to the driver’s secondary side at pin ACLx: As soon as the
voltage on the right side of the 20Ω resistor of Fig. 3 exceeds about 1.3V, the turn-off MOSFET of the driver
stage is progressively switched off in order to improve the effectiveness of the active clamping and reduce the
losses in the TVS. The turn-off MOSFET is completely switched off when the voltage on the right side of the
20Ω resistors approaches 20V (measured with respect to COMx). In parallel IGBT operation with the use of
only one driver core, Advanced Active Clamping needs to control all parallel-connected IGBTs/MOSFETs. A
separate feedback to every gate is required according to Fig. 3.
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Application Note
Fig. 3 Active clamping by paralleling three IGBTs/MOSFETs with one common gate driver core
It is recommended to use the circuit shown in Fig. 3 for parallel operation with one gate driver core
(exceptions: 2SC0635T and 1SC0450, for which D 3x and the 20Ω resistors are already included in the driver
core and therefore need not be used externally). For dimensioning the TVS, R aclx , C aclx , D 3x and D 4x , please
refer to the corresponding application manual /1/. Note that at least one of the series connected TVS must be
of bidirectional type.
V CEsat in parallel operation with one driver core
In general, Power Integrations recommends the use of only one V CEsat detection circuit by using only one
central gate driver core for paralleled IGBTs/MOSFETs, as this is sufficient to efficiently protect the system.
The V CEsat detection is connected to one of the parallel-connected IGBTs/MOSFETs. All paralleled switches
desaturate at the same time in the short-circuit condition. The maximum short-circuit current is limited by the
power semiconductors inherently.
It is not recommended to connect auxiliary collectors of paralleled high-side IGBTs, as:
•
A large offset current may flow and
•
oscillations may occur.
Moreover, the measurement of overcurrent via the V CEsat detection is not recommended.
Fig. 4 V CEsat detection by paralleling three IGBTs with one gate driver core
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AN-1101
Application Note
Direct paralleling
Parallel-connected IGBTs/MOSFETs are conventionally driven by a common driver, with individual gate and
emitter (source) resistors for each switch (refer to last paragraph). An alternative approach for driving parallelconnected power modules is to use an individual driver for each module (direct paralleling). This driving option
is available for all driver cores with electrical interface considered in this Application Note.
If direct paralleling of SCALE-2 drivers is required, please refer to the Application Note AN-0904 /4/.
Application Circuits
Minimum pulse suppression for inputs INA and INB
SCALE-2 gate drivers with electrical interface feature very fast signal propagation delays of typically <90ns.
This includes a minimum pulse suppression time of 35ns. To avoid false gate switching caused by potential
EMI, the inputs INA and INB may be equipped with additional filters. Fig. 5 illustrates how to increase the
minimum pulse suppression time for driver cores with electrical interface if the SCALE-2 internal minimum
suppression time is not long enough.
Fig. 5 shows that it is not recommended to apply a RC network directly to INA or INB as the jitter of the
propagation delay may increase considerably. The use of a Schmitt-trigger is recommended to avoid this
drawback.
Note that it is recommended to parallel the inputs INA/INB of the drivers after the Schmitt-triggers if direct
paralleling is used together with minimum pulse suppression. The use of a Schmitt-trigger for each driver core
is not recommended by direct paralleling as the delay divergence of the Schmitt-triggers may be too high,
leading to an excessive dynamic current imbalance during IGBT commutation.
Fig. 5 Minimum pulse suppression for INA and INB for SCALE-2 driver cores
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Application Note
The R 1 /C 1 combination together with a 15V Schmitt-trigger create minimum pulse suppression. As an
example, the Schmitt-trigger input hysteresis is 5V if the turn-on level is 10V and the turn-off level is 5V. If
INx turns on with 15V logic, the capacitor C 1 is charged by R 1 . When the voltage across C 1 reaches 10V, the
Schmitt trigger switches. If INx becomes low (turn-off command) and the voltage across the capacitor C 1 falls
below 5V, the Schmitt trigger switches.
The minimum pulse suppression time T min,on at turn-on can be calculated as follows:
Tmin , on = R1 ⋅ C1 ⋅ ln(
VDD
)
VDD − VTH , high
Eq. 1
where V TH,high is the upper Schmitt-trigger threshold and V DD is the logic level of INx.
The minimum pulse suppression time T min,off at turn-off can be calculated as follows:
Tmin , off = R1 ⋅ C1 ⋅ ln(
VDD
)
VTH ,low
Eq. 2
where V TH,low is the lower Schmitt-trigger threshold and V DD is the logic level of INx.
Example:
•
T min,on =500ns: R 1 =3.3kΩ, V TH,high =10V, VDD=15V, C 1 = 138pF
•
T min,off =1μs: R 1 =3.3kΩ, V TH,low =5V, VDD=15V, C 1 = 276pF
Increase of the noise immunity at inputs INA and INB (excluding 2SC0635T)
Most SCALE-2 gate driver cores with electrical interface turn on the corresponding channel when INA/INB
reaches a threshold voltage of about 2.6V (exception: 2SC0635T). The turn-off threshold voltage is about
1.3V, resulting in a hysteresis of 1.3V. In some applications with very high noise interference voltages (EMI),
or when long cables are used, increasing the input threshold voltage helps to avoid irregular switching events.
For this purpose, a voltage divider R 2 /R 3 is placed as close as possible to the gate driver core according to Fig.
6. The minimum distance between the voltage divider R 2 /R 3 and the gate driver is essential to avoid inductive
coupling on the PCB layout.
Fig. 6 Increased threshold voltages INA and INB with SCALE-2 gate driver cores
Example: Setting R 2 =3.3kΩ, R 3 =1.2kΩ and INA=15V at turn-on. Without R 2 and R 3 , the gate driver turns on
as soon as INA reaches 2.6V. The voltage divider increases the turn-on threshold voltage to about
10.5V. The turn-off threshold voltage is now about 5.0V. In this example, the INA and INB signal
drivers have to provide ~3.5mA during the IGBT on-state.
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AN-1101
Application Note
Use of external optical interface with SCALE-2 gate drivers with internal
electrical interface
For applications requiring optical PWM inputs and fault outputs, Power Integrations’ products permit different
solutions. Beside standard plug-and-play driver solutions for high-voltage IGBTs and the driver core 1SC0450,
an alternative solution is to just use an optical interface in front of a SCALE-2 gate driver core with an
electrical interface. Fig. 7 shows an example of how to drive a SCALE-2 driver core with a standard AVAGO
HFBR type (for other manufacturers, e.g. TOSHIBA, PANASONICS, … contact the Power Integrations support
service). A Schmitt-trigger (supplied with 5V) inverts the output signal of the HFBR-2522ETZ into a 5V logic
signal. This signal drives the SCALE-2 gate driver core. The open drain fault outputs SO1 and SO2 have a 1kΩ
pull-up resistor to drive the optical interface. The light is on during the normal condition and off in the fault
condition. The diode current during normal operation is about 15mA. During the fault condition, this current
flows via open drain SO1 and/or SO2, respectively. The maximum allowed SO1/SO2 load current is 20mA.
Fig. 7 Optical interface driving a SCALE-2 gate driver core
Only direct mode is recommended (MOD is connected to GND) with the use of two or more SCALE-2 gate
driver cores with direct paralleling (Fig. 8). The inputs INA and INB of each driver are connected in parallel.
The SOx fault outputs can be connected together or each can be wired to a fiber-optics interface. A pull-up
resistor must be placed as close as possible to the gate driver core. This resistor is calculated for a diode
current of approximately 13mA and a maximum open collector current of 20mA per channel.
Note that both pins TB are paralleled. The resistor value of R B given in the data sheet /2/ must therefore be
divided by two to obtain the corresponding blocking time. The power supply of the Schmitt-trigger must be
5V.
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Application Note
Fig. 8 Optical interface driving paralleled SCALE-2 gate driver cores (example with 2SC0435T)
Note that both circuits of Fig. 7 and Fig. 8 cannot be used with 2SC0635T, as the input thresholds of INA and
INB are higher (adjustment for 15V logic required).
Half-bridge mode
The MOD pin – if available – can be used to configure direct or half-bridge mode on dual-channel drivers
(refer to corresponding application manual /1/ for more information).
It is recommended to place the components R m and C m (refer to the corresponding application manual /1/ or
to Fig. 11) as close as possible to the MOD pins and to avoid big loops.
The dead time tolerance may vary from product to product and from the dead time setup and is also
dependent on the target PCB layout. A tolerance of approximately ±15% may be expected.
Moreover, it is impermissible to change between direct and half-bridge mode, or the reverse during driver
operation. This may result in high-frequency burst pulses that may destroy the driver.
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Application Note
External implementation of half-bridge mode
Dead times between both channels of a driver core can also be generated with external circuitry using the
direct mode of the SCALE-2 driver. This can be useful if the required dead time length is outside the range
provided by the SCALE-2 technology (about 0.6-4.1µs) or when tighter timing precision is needed.
The PWM pattern, including the required dead times, can be generated using digital circuits (e.g. µP, FPGAs,
CPLDs) or with discrete circuits. Fig. 9 below shows a circuit example that generates dead times in a similar
way as the SCALE-2 technology, using an enable signal and a switching signal.
Fig. 9 Recommended circuit for the external generation of half-bridge dead times
The required dead times T D can be approximately set up with the components R and C considering the
thresholds of the AND gates used:
TD ≈ R ⋅ C ⋅ ln(
VDD
VDD
)
− VTH ,high
Eq. 3
where V TH,high is the upper Schmitt-trigger threshold and V DD is the logic level of the Schmitt-trigger/AND
gates, that may be 5V…15V. It is recommended to use high-speed switching diodes for the diodes D.
Example: A half-bridge dead time of T D ≈7.7µs can be set up with R=4.7kΩ and C=1.5nF (V DD =15V,
V TH,high =10V)
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Application Note
External implementation of minimum channel interlock time
When dead times are generated externally using the direct mode of the SCALE-2 driver cores, it is possible to
implement an interlock circuit according to Fig. 10 that avoids simultaneous switching of the inputs/outputs,
even if the generated switching signals are incorrect.
Fig. 10 Recommended circuitry for setting a minimum interlock time
The circuit shown in Fig. 10 does not significantly modify the switching signals INA* and INB* if the minimum
programmed interlock time T I is not undercut:
VDD
TI ≈ R ⋅ C ⋅ ln(
)
VDD − VTH ,high
Eq. 4
where V TH,high is the upper Schmitt-trigger threshold and V DD is the logic level of the Schmitt-trigger/AND
gates, that may be 5V…15V. It is recommended to use high-speed switching diodes for the diodes D.
If the signals INA* and INB* have a dead time which is lower than the programmed minimum interlock time
T I , the dead time between both channels is automatically extended to T I .
If both signals INA* and INB* are high at the same time, both channels are turned off.
Note that the use of external components increases the overall propagation delay time of the gate driver.
Use of SOx fault outputs
The longer the distance to the microcontroller, the more EMI-sensitive does the SOx line become. When no
fault condition is detected, the SOx output has high impedance. Voltage spikes can therefore easily be
induced.
Power Integrations recommends the use of the circuit shown in Fig. 11 if long cable distances are necessary or
if the SOx current capability of 20mA is not sufficient. The MOSFETs T11/T12 protect the driver’s SOx outputs
from EMI influences. It is additionally recommended to use pull-down resistors on the host controller cable
side to provide safe logic in case the SOx signal should not be connected properly (e.g. broken cable). Note
that the pull-down resistor values must not be too low, as a voltage divider is built with the MOSFET pull-up
resistors.
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Application Note
The SOx driving current can be easily increased by reducing the 2.7k pull-up resistor values of the MOSFETs.
Fig. 11 Use of SOx fault signals over long distances
Note that a protection circuit for the SOx pins as well as a pull-up resistor of 10kΩ is available on the driver
cores 2SC0635T and 1SC0450.
Use of gate resistors
Most of the SCALE-2 driver cores feature separated paths GHx and GLx to connect the turn-on and turn-off
gate resistors. It is mandatory to use separated turn-on and turn-off gate resistors, as shown in Fig. 12.
Increased power losses and oscillations may occur if GHx is directly connected to GLx. However, this does not
apply to 2SC0106T.
Fig. 12 Use of gate resistors with the terminals GHx and GLx
Moreover, it is necessary for several reasons to keep the inductance of the gate loop as small as possible:
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Application Note
•
High gate-loop inductances will alter the switching performance of the IGBT. In particular, faster
commutation may occur during turn-on, which could cause SOA violation of the corresponding freewheeling diode.
•
The use of high-inductance resistors (e.g. wire wound resistors) is impermissible. It is recommended
to use high-power proofed 1206 SMD resistors (e.g. CRCW1206 resistors from Vishay) or leaded metal
film resistors (e.g. PR02 or PR03 from Vishay) and to measure the temperature increase of the gate
resistors at the target switching frequency to avoid thermal overload. A maximum temperature
increase of 40K or lower is usually recommended. Moreover, the peak power capability of the gate
resistors must not be exceeded.
•
Reducing the gate loop inductance reduces possible coupling from external magnetic fields into the
gate circuit. Such coupling may alter the gate driver performance, generate oscillations or even lead to
the IGBT SOA being exceeded under certain circumstances. If possible and/or required, shielding
planes can be used to reduce the influence of external magnetic fields.
VEx terminal characteristics
VEx corresponds to the emitter potential. It is an internally generated potential of the SCALE-2 ASIC. During
normal operation, the voltage between the pins VISOx and VEx is regulated to a nominal value of 15V. This is
done by means of a SCALE-2 internal current source and voltage measurement in the secondary ASIC IGD. Its
maximum sink/source capability is limited to ±2.5mA in order to avoid thermal overloading of the ASIC during
operation.
If the secondary voltage between VISOx and COMx begins to fall, the voltage between VISOx and VEx
remains constant at 15V in a first step. The voltage between VEx and COMx is reduced up to about 5.5V. If
the voltage still falls from VISOx to COMx, the voltage from VEx to COMx remains constant at 5.5V and the
voltage from VISOx to VEx begins to fall. This function ensures a proper turn-off of IGBTs even in the event of
a supply under-voltage.
No static load should be applied between VISOx and VEx or between VEx and COMx in order not to disturb the
15V regulation between VISOx and VEx. A static load can be applied between VISOx and COMx if necessary
(e.g. supply load for external electronic functions). This is illustrated in Fig. 13.
Fig. 13 External loading of VISOx, VEx and COMx (example with 2SC0435T)
Note that it is not permitted to insert a resistor between the gate and emitter as shown in Fig. 14, as this
would also statically load the 15V regulator.
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Application Note
Fig. 14 Impermissible resistor between gate and emitter (example with 2SC0435T)
The voltage at VEx (and therefore the gate-emitter voltage) can also be set to a specific custom value by
means of external circuitry. The internally controlled 2.5mA DC current at VEx is then drawn/sourced by
external components such as a combination of a resistor with a Zener diode or by a linear regulator. When
realizing deviating voltage levels with external circuitry, several points have to be observed:
•
The voltage between VISOx and VEx as well as VEx and COMx must not exceed 20V. The voltage
between VISOx and VEx must additionally be limited to 17.5V for drivers which feature the Soft Shut
Down function (SCALE-2+).
•
The voltage between VISOx and VEx as well as VEx and COMx must not be set to a value which
triggers the under-voltage monitoring (UVLO). For specific values, refer to the respective data sheet
/2/ for the gate driver.
•
It is impermissible to switch VEx to COMx potential when the driver is supplied with power.
If voltage levels that violate the above rules are required, please contact the Power Integrations’ support
service.
Required blocking capacitors C1x and C2x
The SCALE-2 gate drivers are equipped with blocking capacitors on the secondary side of the DC/DC converter
(for values, refer to the corresponding driver data sheet /2/). These blocking capacitors allow fast charging
and discharging of the gate capacitance of power semiconductors (which is characterized by the gate charge)
via the N-channel MOSFET driver stages.
For IGBTs or MOSFETs, a minimum total blocking capacitance of 3µF is recommended for every 1µC of gate
charge, unless otherwise specified in the corresponding application manual /1/. The missing blocking
capacitance on a SCALE-2 driver core must be added externally.
The blocking capacitors must be placed between VISOx and VEx (C 1x in Fig. 15) as well as between VEx and
COMx (C 2x in Fig. 15). They must be connected as close as possible to the driver’s terminal pins with minimum
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Application Note
inductance. It is recommended to use the same capacitance value for both C 1x and C 2x (IGBT mode). Ceramic
capacitors with a dielectric strength >20V are recommended. Note that during power-on, the capacitors are
charged with a limited current thanks to the soft start function implemented in the SCALE-2 gate drivers.
If the required capacitances C 1x or C 2x exceed the maximum value given in the corresponding description and
application manual /1/, please contact Power Integrations' support service.
Note that the use of electrolytic capacitors such as tantalum capacitors is not recommended.
Fig. 15 Use of external blocking capacitors on the secondary side (example with 2SC0435T)
VCEsat detection with SCALE-2 gate driver cores (excluding 2SC0108T)
Desaturation protection with resistors (for 650V-1700V driver cores)
The collector sense must be connected to the IGBT collector or MOSFET drain with the circuit shown in Fig. 16
and Fig. 17 in order to detect an IGBT or MOSFET short-circuit.
During an IGBT off-state, the driver’s internal MOSFET connects pin VCEx to pin COMx. The capacitor C ax is
then pre-charged/discharged to the negative supply voltage, which is about -10V referred to VEx (red circle in
Fig. 16). During this time, a current flows from the collector (blue circle in Fig. 16) via the resistor network and
the diode BAS416 to VISOx. The current is limited by the resistor chain.
It is recommended to dimension the resistor value of R vcex in order to obtain a current of about I Rvcex =0.6-1mA
flowing through R vcex (e.g. 1.2-1.8MΩ for V DC-LINK =1200V). A high-voltage resistor as well as series-connected
resistors may be used. It must be ensured that the resistors R vcex are not overloaded in either voltage or
thermal respects:
•
A maximum temperature increase of 40K or lower is usually recommended in the worst case condition.
•
The maximum voltage withstand capability of the resistors used must not be exceeded. Moreover, the
minimum creepage distance relating to the application must be considered.
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Application Note
I Rvcex =
(VCEx − VISOx)
RVCEx
Eq. 5
The reference voltage is set by the resistor R thx . It is calculated via the reference current (typically 150uA) and
the reference resistance R thx (green circle in Fig. 16)
Vrefx = 150 µA ⋅ Rthx
Eq. 6
Power Integrations recommends the use of R thx =68kΩ to detect short-circuits. Lower resistance values make
the system more sensitive and do not provide any advantages in the case of desaturated IGBTs (short-circuit).
Note that the resistor R thx is already available on some driver cores such as 2SC0106T, 2SC0108T2D0-07,
2SC0108T2D0-12, 2SC0635T and 1SC0450.
Fig. 16 V CE desaturation protection with resistors (600V-1700V IGBT modules)
At IGBT turn-on and in the on-state, the above-mentioned MOSFET turns off. While V CE decreases (blue curve
in Fig. 16), C ax is charged from the COMx potential to the IGBT saturation voltage (red curve in Fig. 16). The
time required to charge C ax depends on the DC bus voltage, the value of the resistor R ax and the value of the
capacitor C ax . For 1200V and 1700V IGBTs it is recommended to set R ax =120kΩ. For 600V IGBTs the
recommended value is R ax =62kΩ. The resulting response time is given in the corresponding application
manual /1/. It is valid in the short-circuit condition for a minimum DC-link voltage of about 25V*R vcex /R ax . Note
that the response time will increase for lower DC link voltages. However, the energy dissipated in the IGBT in
the short-circuit condition generally remains at the same level or is even lower.
The diode D 1 in Fig. 17 must have a very low leakage current (in particular at elevated ambient/junction
temperatures) and a blocking voltage >40V (e.g. BAS416). Schottky diodes must be explicitly avoided.
Fig. 17 Recommended circuit for desaturation protection with resistors (600V-1700V IGBT modules)
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Application Note
Note: The related components C ax , R ax , R thx and D 1 must be placed as close as possible to the driver. A large
collector-emitter loop must also be avoided. Furthermore, no traces or planes, which show unstable potentials
(e.g. gate signals), must cross these components. Traces and planes with stable potentials (e.g. with VISOx,
VEx or COMx potential) are recommended instead.
It is recommended to implement a response time (short-circuit time) which is high enough to avoid false
tripping of the desaturation protection during IGBT turn-on. If the desaturation protection function is set up
with an insufficiently long response time, a fault may be triggered during IGBT turn-on, especially in cases
where the V CE voltage drop time is low (usually at high DC-link voltages, high collector currents and junction
temperatures). The ruggedness of the design can be tested in the following way:
•
The IGBT must be turned on at the highest DC-link voltages, collector current and junction
temperature (e.g. using the double pulse technique).
•
If no fault is generated, the sensitivity of the desaturation protection function can be increased by
reducing the capacitance value of C ax and/or reducing the driver supply voltage VDC. This allows the
design margin to be checked.
•
Alternatively, the turn-on speed of the IGBT module can be artificially reduced by increasing the
turn-on gate resistance to check the design margin.
If the design margin is insufficient, it is recommended to increase the response time. Note, however, that the
maximum allowed short-circuit time of the IGBT module must not be exceeded under the conditions stated in
the data sheet of the IGBT module (if in doubt, please consult the supplier of the IGBT module).
For driver cores of voltage classes higher or equal to 3300V, the recommended circuit for desaturation
protection can be found in the corresponding application manual /1/.
Desaturation protection with sense diodes (only for 650V-1700V driver cores)
SCALE-2 technology also provides desaturation protection with high-voltage diodes as shown in Fig. 18.
However, the use of high-voltage diodes has some disadvantages compared to the use of resistors:
•
Common-mode current relating to the rate of change dv ce /dt of the collector-emitter voltage: Highvoltage diodes have large junction capacitances C j . These capacitances in combination with the
dv ce /dt generate a common-mode current I com flowing in and out of the measurement circuit.
I com = C j ⋅
dvce
dt
Eq. 7
•
Price: High-voltage diodes are more expensive than standard 0805/150V or 1206/200V SMD resistors.
•
Availability: Standard thick-film resistors are comparatively easier to source on the market.
•
Limited robustness: The reaction time does not increase at lower V CE levels. Consequently, false
triggering may occur at higher IGBT temperatures, higher collector currents, resonant switching or
phase-shift PWM, particularly when the reference voltage V thx is set lower than about 10V. The upper
limit of the reference voltage is restricted to about 10V, which may lead to limited IGBT utilization:
The collector current may be limited to values smaller than twice the nominal current, or the shortcircuit withstand capability may be reduced.
During the IGBT off-state, D 4 (and R ax ) sets the VCEx pin to COMx potential, thereby pre-charging/discharging
the capacitor C ax to the negative supply voltage, which is about -10V referred to VEx. At IGBT turn-on, the
capacitor C ax is charged via R ax to 15V. When the IGBT collector-emitter voltage drops below that value, the
voltage of C ax is limited via the high-voltage diodes D 1 and D 2 . The voltage across C ax can be calculated by:
Vcax = VCEsat + VF ( D1) + VF ( D 2 ) + 330Ω ⋅
15V − VCEsat − VF ( D1) − VF ( D 2 )
Rax + 330Ω
Eq. 8
The reference voltage V refx needs to be higher than V cax . It is set up by the resistor R thx and can be calculated
via the reference current (typically 150uA) and the reference resistance R thx :
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Page 18
AN-1101
Application Note
Vrefx = 150 µA ⋅ Rthx
Eq. 9
Fig. 18 Recommended circuit for desaturation protection with sense diodes
It is recommended to use standard rectifier diodes such as 1N4007 for D 1 and D 2 (2 diodes for 1200V IGBTs,
3 diodes for 1700V IGBTs). D 3 and D 4 must be high-speed diodes (e.g. BAS316). Schottky diodes must be
avoided.
The value of the resistance R ax can be calculated with the following equation in order to program the desired
response time T ax at turn-on:
Rax [kΩ] ≈
1000 ⋅ Tax [ µs ]
15V + VGLx
Cax [ pF ] ⋅ ln(
)
15V − Vrefx
Eq. 10
V GLx is the absolute value of the turn-off voltage at the driver output. It depends on the driver load and can be
found in the driver data sheet /2/.
Recommended high-voltage diodes D 1 /D 2 and values for R ax and C ax are:
•
High-voltage diodes:
•
R ax =24kΩ…62kΩ
•
C ax =100pF…560pF
1x 1N4007 for 650V IGBTs
2x 1N4007 for 1200V IGBTs
3x 1N4007 for 1700V IGBTs
Note that C ax must include the parasitic capacitance of the PCB and the diode D 3 .
Note also that the instantaneous V CE threshold voltage is determined by the voltage at pin REFx (150μA
through R thx ) minus the voltage across the 330Ω resistor as well as the forward voltages across D 1 and D 2 .
Note that the minimum off-state duration should not be shorter than about 1µs in order not to significantly
reduce the response time for the next turn-on pulse.
Example: A resistor of R ax ≈46kΩ must be used to define a response time of 6μs with C ax =150pF, R thx =33kΩ
and V GLx =9V.
It is recommended to implement a response time (short-circuit time) which is high enough to avoid false
tripping of the desaturation protection during IGBT turn-on. If the desaturation protection function is set up
with an insufficiently long response time, a fault may be triggered during IGBT turn-on, especially in cases
where the V CE voltage drop time is low (usually at high DC-link voltages, high collector currents and junction
temperatures). The ruggedness of the design can be tested in the following way:
•
The IGBT must be turned on at the highest DC-link voltages, collector current and junction
temperature (e.g. using the double pulse technique).
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Page 19
AN-1101
Application Note
•
If no fault is generated, the sensitivity of the desaturation protection function can be increased by
reducing the capacitance value of C ax and/or reducing the driver supply voltage VDC. This allows the
design margin to be checked.
•
Alternatively, the turn-on speed on the IGBT module can be artificially reduced by increasing the
turn-on gate resistance to check the design margin.
If the design margin is insufficient, it is recommended to increase the response time. Note, however, that the
maximum allowed short-circuit time of the IGBT module must not be exceeded under the conditions stated in
the data sheet of the IGBT module (if in doubt, please consult the supplier of the IGBT module).
Note that the desaturation protection circuit with sense diodes is not recommended for driver cores of voltage
classes higher or equal to 3300V.
Disable VCEsat detection by SCALE-2 (excluding 2SC0106T and 2SC0108T)
To disable the V CEsat measurement of gate driver cores, a resistor with a minimum value of 1kΩ needs to be
placed between VCEx and COMx.
The reference resistor R thx (if available) may be chosen between 33kΩ and infinity, i.e. the REFx pin may be
left open.
Fig. 19 Disabling the V CEsat detection by SCALE-2 driver cores (example with 2SC0435T)
www.power.com/igbt-driver
Page 20
AN-1101
Application Note
Disabling the Advanced Active Clamping
To disable the Advanced Active Clamping function, the ACLx input needs to be left open. Refer to the
corresponding application manual /1/.
Fig. 20 Disabling Advanced Active Clamping by SCALE-2 (example with 2SC0435T)
Rail-to-rail output and gate voltage clamping
Power Integrations’ SCALE-2 gate drivers use an N-channel output stage like that shown in Fig. 21. After
charging the power semiconductor gate input, the voltage drop over the N-channel MOSFET is nearly zero.
SCALE-2 drivers therefore feature rail-to-rail gate outputs.
A rail-to-rail output has several advantages in driving power semiconductors. The first one is that the VISOx
voltage can be regulated to 15V. By using a Schottky diode (D 5 in Fig. 21), the gate voltage is clamped to the
regulated 15V. This avoids an increase of the external gate-emitter voltage and consequently lowers the IGBT
short-circuit current I SC and energy, as the former is highly dependent on the gate-emitter voltage V GE :
I SC = f (VGE )
Eq. 11
The gate clamping described here is much more efficient than gate-emitter clamping with transient voltage
suppressors. The latter does not allow the gate-emitter voltage to be limited in the short-circuit condition to
15V, as some clamping voltage reserve must be applied in view of the component tolerances and temperature
dependence in order to avoid static conduction and therefore overload at V GE =15V.
A second advantage is that parasitic power semiconductor turn-on can be prevented when the gate driver
power is off. In that case, the gate-emitter voltage on the power semiconductor is zero. If the collector-emitter
voltage V CE increases at a given dV CE /dt, a current I g will flow in the gate loop via the Miller capacitance C Miller :
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Page 21
AN-1101
Application Note
I g = CMiller ⋅
dVCE
dt
Eq. 12
With the use of D 5 in Fig. 21 the current I g will charge the blocking capacitors C 12 and C 22 . The voltage over
C 12 and C 22 will generally remain low. A parasitic turn-on of the power semiconductors is therefore not
possible. This function can be also used for STO (Safe Torque Operation).
Fig. 21 Rail-to-Rail output and gate clamping (example with 2SC0435T)
Note that the gate clamping described here is not possible on 2SC0108T drivers since VISOx is not available
externally. Gate-emitter clamping with transient voltage suppressors should be used instead.
Paralleling a dual-channel driver to a single output
Dual-channel driver cores can be configured to a single driver core with the double output power and gate
current (exception: drivers featuring and using SCALE-2+ Soft Shut Down functionality).
It is recommended to proceed in the following way and as shown in Fig. 22 to merge both driver channels to
one logical channel (excluding 2SC0108T):
•
Direct mode must be selected (MOD pin pulled to GND).
•
Both input signals INA and INB must be connected together.
•
Both secondary-side emitter potentials VE1 and VE2 must be connected together.
•
It is recommended to disable the desaturation protection for one channel while it is enabled on the
other channel.
•
If available, the reference value V th2 is set up to 10V with R th2 =68kΩ.
•
Both channels need gate resistors to decouple the driver output stages. The driver channels are
connected together on the IGBT gate side of the gate resistors. The turn-on and turn-off gate
resistors need to be the same for both channels with a tolerance value of ≤5% (1% recommended).
•
The active clamping controls the turn-off driver stages in the driver core at turn-off. Each of the
Advanced Active Clamping pins ACLx of both channels must therefore be connected to a 20Ω resistor
according to Fig. 22 (The 20Ω resistors as well as D 3x must be omitted on 2SC0635T, as these
components are already available on the driver core).
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Page 22
AN-1101
Application Note
•
Both fault signals SO1 and SO2 can be connected to a single fault signal SO.
•
As soon as a fault is detected at SO, the PWM input signal must be pulled to GND in order to turn-off
any driver channel that may not already be turned off. Omitting this point could lead to thermal
damage to the driver, as one driver channel is turned off in the fault condition and the other remains
turned on, leading to high power losses in the driver. The PWM input should not be activated before
the SO fault signal is high again, i.e. no fault signal is available. This is important in order to avoid only
one channel switching, as the blocking time of both driver channels is not exactly the same. Additional
restrictions may apply when using 2SC0635T if the CSHDx pin is used (refer to the corresponding
application manual /1/).
Fig. 22 Paralleling a dual-channel driver to a single output (example with 2SC0435T)
Paralleling the two gate driver channels on 2SC0108T is similar to the procedure for all other SCALE-2 gate
driver cores. The main difference is that no Advanced Active Clamping is available. If (basic) active clamping is
used, the transient voltage suppressor chain is connected directly to the gate (see Fig. 23).
Fig. 23 Paralleling both driver channels of 2SC0108T
Note that the two driver channels of gate drivers featuring SCALE-2+ Soft Shut Down cannot be run in parallel
if the Soft Shut Down function is used. The efficiency of the Soft Shut Down functionality can otherwise not be
guaranteed.
www.power.com/igbt-driver
Page 23
AN-1101
Application Note
Disabling one channel for chopper applications
In some cases, a single gate driver is required, such as for chopper operation, e.g. a break chopper in a DClink bus. A single gate driver is not always available or commercially viable for such applications. A dualchannel gate driver core can therefore be used where one channel has to be disabled.
It is recommended to proceed in the following way to disable one driver channel:
•
The corresponding signal input INx must be pulled to GND.
•
The fault feedback SOx must be pulled to VCC with a 15kΩ resistor.
•
Direct mode (if available) must be selected (MOD pin pulled to GND).
•
The secondary side of the channel can be left open (not connected).
Position of the Gate Driver in the Converter
The temperature as well as both magnetic and electric fields can influence the functionality of the signal
electronics. Choosing the right position for the gate driver in the power electronics system helps to prevent
system dysfunction and EMI effects.
Power Integrations’ SCALE-2 gate drivers are generally designed for ambient temperatures of up to 85°C.
Excessive temperatures mainly limit the DC/DC power. In the worst case, the DC/DC transformer core goes
into saturation and the gate driver core is destroyed. In converters where the gate driver is placed close to the
heat sink or the power semiconductors, it is important to check that the maximum permissible temperature
around the driver is not exceeded.
Furthermore, high currents generate high magnetic fields and high voltages generate high electric fields.
Combined with high switching speeds, these fields represent a harsh environment for the signal electronics
available on the gate drivers. This point is further detailed below.
Driver placement on top of 17mm IGBT modules or close to high magnetic
fields
17mm IGBT modules are becoming increasingly popular in power electronics applications. Manufacturers like
Danfoss Silicon Power, Fuji, Infineon, IXYS, Mitsubishi and Semikron offer a range of 17mm packages on the
market.
Several SCALE-2 driver cores have been optimized to work in environments with high magnetic fields. They
can be used directly on top of IGBT modules without problems. These drivers are:
•
2SC0106T – the entire driver family
•
2SC0108T2F1-17, 2SC0108T2G0-17, 2SC0108T2H0-17, 2SC0108T2D0-07 and 2SC0108T2D0-12
•
2SC0435T2F0-17, 2SC0435T2F1-17, 2SC0435T2G1-17, 2SC0435T2H0-17
•
2SC0650P – the entire driver family
•
1SC2060P – the entire driver family
•
1SC0450 – the entire driver family
Other gate drivers, as those listed here, are not recommended to be used directly on top of IGBT modules,
especially on top of 17mm IGBT modules. Magnetic field coupling during turn-on and turn-off events and
especially during IGBT short circuit can lead to their malfunction.
www.power.com/igbt-driver
Page 24
AN-1101
Application Note
AC and DC bus bar
Laminated DC bus bars generally produce low external magnetic and electric fields due to their laminated
structure. A gate driver can therefore be located on top or underneath the DC bus as long the insulation or the
clearances are sufficient.
However, the situation concerning the AC or phase leg bus bar is different. The output current generates a
magnetic field around the bus bar and the rate of change of the electric field is generally high. If the gate
driver is placed directly underneath or above the AC bus bar, shielding may be necessary. This can be an iron
plate (shielding for low frequencies) or a thick aluminum or copper plate (shielding for high frequencies). The
eddy current flowing in the shield will partially compensate for the magnetic field generated near the gate
driver.
However, it is usually recommended to maintain a minimum distance (several cm are generally sufficient)
between the AC bus bar and the gate driver core to reduce the effect of the magnetic field on the driver.
Generally speaking, the closer the conducting current and the signal electronics are to each other, the higher
is the risk of electromagnetic influences.
PCB Layout
SCALE-2 driver cores are sophisticated products that require properly designed PCB layouts in order to work
efficiently and to deliver full performance. Stripboards (“Veroboards”) must therefore not be used together
with SCALE-2 driver cores. It is usually recommended to use 4-layer PCBs. Two-layer PCBs may also be used,
but the performance and/or flexibility are then reduced.
PCB thickness
Power Integrations recommends using a PCB thickness of 1.55mm or higher. The typical pin length of 2.54mm
of many of the SCALE-2 driver cores has been optimized for the use of 1.55mm PCB thickness.
It is recommended to use drivers with longer pins when using PCB thicknesses of 2mm or higher to avoid
soldering problems during production. The following drivers have longer pins:
3.1mm
•
2SC0108T2G0-17
•
2SC0435T2G0-17, 2SC0435T2G1-17
5.84mm
•
2SC0108T2C0-17, 2SC0108T2F0-17, 2SC0108T2F1-17
•
2SC0435T2C0-17, 2SC0435T2E0-17, 2SC0435T2F0-17, 2SC0435T2F1-17
•
2SC0650P2C0-17
•
1SC2060P2A0-17
•
2SC0535T2A0-33, 2SC0535T2A1-33
•
2SC0635T2A0-45, 2SC0635T2A1-45
•
1SC0450V2A0-45, 1SC0450V2A0-65, 1SC0450E2A0-45, 1SC0450E2A0-65
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Page 25
AN-1101
Application Note
Separation of areas with different high-voltage potentials
One important rule for PCBs designed for power electronics applications is that layers relating to different
high-voltage potentials must never overlap as shown in Fig. 24. If this is omitted, large coupling capacitances
between the different high-voltage potentials will result, leading to excessive common-mode current I com on
the PCB during switching operation. Moreover, the long-term isolation reliability may become problematic.
Fig. 24 PCB layout of SCALE-2 driver adapter boards
Equations 13 and 14 describe how to calculate common-mode currents I com relating to overlapping planes in
different PCB layers during IGBT commutation with a rate of change of the collector-emitter voltage of
dV CE /dt:
C PCB = ε 0 ⋅ ε r ⋅
A
l
Eq. 13
A is the area where high-voltage potentials overlap, l is the distance between both PCB layers, ε r =5, and
ε 0 =8.85pF/m.
I com = C PCB ⋅
dVce
dt
Eq. 14
Not only planes (e.g. ground or emitter potentials) are affected by these rules. All other signal lines with large
switching potential differences must also satisfy this rule. A high-side collector potential must therefore – as an
example – never cross a low-side gate signal on the PCB layout.
It is mandatory to implement sufficient clearance and creepage distances as required by the corresponding
standards (refer also to section “Clearance and creepage distances for PCBs”).
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Page 26
AN-1101
Application Note
Use of planes
It is highly recommended to use planes to distribute constant potentials (especially power supplies and
ground) efficiently over the corresponding PCB areas. Additionally, the planes act as magnetic shielding and
strongly reduce the influence of external magnetic fields if they are properly designed.
The layers can be used in the following way (example):
Driver primary side
•
Top Layer:
Components, cooling surface and traces
•
Mid Layer 1:
VCC
•
Mid Layer 2:
VDC
•
Bottom Layer: GND, cooling surface and test points
Driver secondary side(s)
•
Top Layer:
Components, cooling surface and traces
•
Mid Layer 1:
Emitter or VISO
•
Mid Layer 2:
VISO or emitter
•
Bottom Layer: COM, cooling surface and test points
Several planes with different potentials (example emitter and COM) may naturally also be located on the same
layer, if required. Additional planes with other stable potentials, if available (5V, -15V, …), may also be
established.
On the other hand, it is impermissible to build planes with changing potentials, as such planes will generate
coupling capacitances leading to corresponding current flows when potentials are changing. It is also
impermissible to locate planes over areas with changing high-voltage potentials: The complete resistor chain
of the desaturation protection function as well as all TVS for Advanced Active Clamping must always remain
free from planes.
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Page 27
AN-1101
Application Note
Clearance and creepage distances for PCBs
Tab. 1 gives an overview of the required clearance and creepage distances for several IGBT voltage classes.
Several widely used standards are considered. The listed data assumes Pollution Degree 2 (PD2), Overvoltage
Category II (OV II) and standard FR4 PCB material of material category IIIa.
Note that the working voltages given in Tab. 1 do not necessarily correspond those used to design the
corresponding driver cores. Please check the creepage distances given in the specific data sheets /2/.
Voltage
class of
power
module
(V CES )
Standard
System
voltage
Working
voltage
Max.
altitude
of
operation
Impulse
voltage for
functional
insulation
Impulse
voltage for
reinforced
insulation
Min.
clearance
distance
for
functional
insulation
Min.
clearance
distance
for
reinforced
insulation
Min.
creepage
distance for
functional
insulation1)
Min.
creepage
distance for
reinforced
insulation1)
600V
EN 50178
1997-07
424V RMS
400V DC
2000m
3121V
4994V
2.1mm
4.2mm
2.1mm
4.2mm
460V RMS
400V DC
3298V
5277V
2.3mm
4.6mm
2.3mm
4.6mm
1200V
849V RMS
800V DC
5243V
8388V
4.6mm
8.7mm
4.6mm
8.7mm
1700V
1202V RMS
1200V DC
6808V
10893V
6.5mm
12.3mm
6.5mm
12.3mm
3300V
2333V RMS
2500V DC
11334V
18134V
13.0mm
22.8mm
13.0mm
25.0mm
4500V
3182V RMS
3400V DC
14667V
23468V
18.0mm
30.9mm
18.0mm
34.0mm
6500V
4596V RMS
4500V DC
19853V
31764V
25.5mm
45.5mm
25.5mm
45.5mm
424V RMS
400V DC
4000V
6400V
3.0mm
8.0mm
4.0mm
8.0mm2)
460V RMS
400V DC
4000V
6400V
3.0mm
8.0mm
4.0mm
8.0mm2)
849V RMS
800V DC
5000V
8000V
4.0mm
8.0mm
8.0mm
8.0mm2)
1700V
1202V RMS
1000V DC
8000V
12800V
8.0mm
18.0mm
10.0mm
18.0mm2)
3300V
N.a.3)
4500V
N.a.3)
650V
600V
650V
1200V
IEC 60077-1
Ed. 1
1999-10
N.a.3)
6500V
600V
1400m
424V RMS
400V DC
4000V
6000V
3.0mm
5.5mm
3.0mm
5.5mm
460V RMS
400V DC
4000V
6000V
3.0mm
5.5mm
3.0mm
5.5mm
849V RMS
800V DC
6000V
8000V
5.5mm
8.0mm
5.5mm
8.0mm
1700V
1000V RMS
1000V DC
6000V
8000V
5.5mm
8.0mm
5.5mm
10.0mm
3300V
N.a.3)
4500V
N.a.3)
650V
1200V
IEC 60664-1
Ed. 2
2007-04
N.a.3)
6500V
600V
2000m
424V RMS
400V DC
4000V
6000V
3.0mm
5.5mm
3.0mm
5.5mm
460V RMS
400V DC
4000V
6000V
3.0mm
5.5mm
3.0mm
5.5mm
849V RMS
800V DC
6000V
8000V
5.5mm
8.0mm
5.5mm
8.0mm
1700V
1202V RMS
1200V DC
6777V
10844V
6.5mm
12.3mm
6.5mm
12.3mm
3300V
2333V RMS
2500V DC
11129V
17806V
12.7mm
22.0mm
25.0mm
50.0mm
4500V
3182V RMS
3400V DC
14392V
23028V
17.3mm
30.3mm
34.0mm
68.0mm
6500V
4596V RMS
4500V DC
19597V
31356V
24.5mm
44.9mm
45.0mm
90.0mm
650V
1200V
IEC 61800-5-1
Ed. 2
2007-07
2000m
1) If the determined creepage distance is smaller than the respective clearance distance for functional or reinforced insulation, the clearance distance will be chosen for this
particular creepage distance for safety reasons.
2) IEC 60077-1 does not distinguish between functional and reinforced insulation with respect to the creepage distances. The value of the functional insulation is therefore used for
reinforced insulation as long as the respective clearance distance for reinforced insulation is not higher (see also previous footnote).
3) N.a.: Not applicable
Tab. 1 Summary of required creepage and clearance distances according to several standards
Gate driver cores in applications at higher altitudes
The creepage and clearance distances of Power Integrations gate driver cores are determined according to
specific standards (refer to product documentation /1/, /2/), which indicate a maximum altitude of operation
(Tab. 1).
For use of the drivers at higher altitudes, correction factors for the clearances are usually given in the
standards and must be considered.
For example, for an IGBT power module in a voltage class of 1700V, the maximum altitude for a 2SC0108T
driver is 2000m. If the application operates at higher altitudes and the corresponding standards must be
satisfied, the maximum permissible system voltage must be reduced, or else the next larger Power
www.power.com/igbt-driver
Page 28
AN-1101
Application Note
Integrations’ IGBT gate driver is required. Thus, 2SC0435T drivers can operate according to the standards up
to an altitude of 2900m.
Note that neglect of these requirements can lead to destruction of the IGBT drivers and IGBT modules.
Power Integrations’ Reference Designs
Power Integrations has developed several reference designs for SCALE-2 gate drivers. Full documentation and
CAD production data of those designs incl. bill of materials and Gerber files are available for download from
the Power Integrations’ homepage www.power.com/igbt-driver.
www.power.com/igbt-driver
Page 29
AN-1101
Application Note
Typical Application Failures
Impact on the
driver
Effect
Primary-side
DC/DC MOSFET
destroyed or LDI
ASIC destroyed
(2SC0108T)
DC/DC overload
Cause
• Excessive switching frequency
• High noise on INA or INB
• Partial discharge
• Short circuit in gate, emitter,
VEx, VISOx or COMx
• Use of oversized gate/emitter
capacitor C GE
• Excessive gate charge Q g
• LC gate oscillation
• Excessively high ambient
temperature
• Defective ceramic capacitor
LDI ASIC
destroyed
IGD ASIC
destroyed
IGD ASIC
destroyed
Short circuit with
destruction of LDI,
IGD or DC/DC
MOSFET
Delay divergence
of gate signals
between parallel
connected IGBTs
(>25ns) or jitter
>5ns
• VDD>16V
• Pull-up resistor value at SOx
too small
• ESD handling
• Max. isolation voltage of
1700V exceeded
Excessive
Advanced
Active Clamping
feedback
(>3µs)
• Excessive DC-link voltage
• Excessive stray inductances
• VISOx > 30V
Crack of
ceramic
capacitors
Increased initial
propagation
delay
www.power.com/igbt-driver
Corrective Action
• Select next powerful gate driver
or reduce switching frequency
• EMI protection e.g. minimum
pulse suppression
• Mostly PCB layout failure; check
all clearance and creepage
distances
• Assembly or layout failure
• Calculate the power losses for
C GE
• Calculate the power losses for
Qg
• Remove excessive inductance
in the gate loop
• Reduce the ambient
temperature below 85°C
• Avoid mechanical damage by
handling process or bending of
PCB
• Limit VDD to 16V
• Increase the resistor value
• Improve ESD handling
• Reduce V CE overvoltage e.g.
with active clamping or change
to a higher IGBT blocking
voltage
• Overall design failure, change
to higher IGBT blocking voltage
• Improve the DC bus bar
(reduced stray inductance); do
not apply current >40mA
(mean value) to the ACLx pin
• Limit VDC to 16V
• Handling process, mechanical • Careful mechanical handling
destruction; can also happen
and assembly process
in final mechanical assembly
process
• Use of half-bridge mode
• Use of direct mode
• Slow rise and fall times applied • Insert Schmitt-trigger gates to
to driver inputs
INA/INB
Page 30
AN-1101
Application Note
Bibliography
/1/
Description and Application Manual of SCALE™-2 driver cores, Power Integrations
/2/
Data sheets of SCALE™-2 driver cores, Power Integrations
/3/
Application Note AN-0901: Methodology for Controlling Multi-Level Converter Topologies with
SCALE™-2 IGBT Drivers, Power Integrations
/4/
Application Note AN-0904: Direct Paralleling of SCALE™-2 Gate Driver Cores, Power Integrations
/5/
Paper: Safe Driving of Multi-Level Converters Using Sophisticated Gate Driver Technology, PCIM Asia,
June 2013
Note: The Application Notes are available on the Internet at www.power.com/igbt-driver/go/app-note and
the papers at www.power.com/igbt-driver/go/papers
Legal Disclaimer
The statements, technical information and recommendations contained herein are believed to be accurate as
of the date hereof. All parameters, numbers, values and other technical data included in the technical
information were calculated and determined to our best knowledge in accordance with the relevant technical
norms (if any). They may base on assumptions or operational conditions that do not necessarily apply in
general. We exclude any representation or warranty, express or implied, in relation to the accuracy or
completeness of the statements, technical information and recommendations contained herein. No
responsibility is accepted for the accuracy or sufficiency of any of the statements, technical information,
recommendations or opinions communicated and any liability for any direct, indirect or consequential loss or
damage suffered by any person arising therefrom is expressly disclaimed.
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Fax
Email
Website
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+41 32 344 47 40
[email protected]
www.power.com/igbt-driver
© 2011…2015 Power Integrations Switzerland GmbH.
We reserve the right to make any technical modifications without prior notice.
www.power.com/igbt-driver
All rights reserved.
Version 2.1 from 2016-04-14
Page 31
AN-1101
Application Note
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